靶向唾液酸的放射性半抗原免疫制剂177Lu-SBP-DNP的构建及其协同抗肿瘤作用的研究

免疫治疗联合放射治疗能增强抗肿瘤的疗效，但协同模式亟需进一步优化。我们已报道：①半抗原二硝基氟苯（DNP）连接的非天然唾液酸（Sia）能被肿瘤细胞摄取，经Sia代谢途径呈递到细胞表面，招募抗DNP抗体，诱导T细胞对肿瘤的杀灭。②肿瘤细胞高表达Sia,苯硼酸可增强细胞核摄取炔孕酮探针，但在体内其Sia靶向性尚待提高。前期制备了新型Sia配体-胍基苯硼酸（SBP），结果示：SBP能高亲和力、高特异性结合Sia；肿瘤组织高摄取68Ga-SBP，显像清晰。本课题基于此拟：1、采用有机化学反应制备放射性免疫制剂177Lu-SBP-DNP；2、在细胞和动物模型层面，验证SBP介导下能提高肿瘤细胞表面DNP的丰度，同时177Lu对肿瘤内照射，增强联合杀伤肿瘤的作用；3、ECT显像、病理检查，确认协同治疗优势和作用机制。达到诊疗一体化、免疫-放射协同杀伤肿瘤的目的，为开发一种新型肿瘤治疗方法奠定实验基础。

Recently, studies have found that combination of radiotherapy and immunotherapy can enhance the anti-tumor effect, but its treatment model needs further study. Our previous studies demonstrated that ：① hapten dinitrophenyl (DNP) modified sialic acid (Sia) was absorbed by tumor cells and conjugated on the surface of tumor cells through Sia metabolic pathway, and then antibodies were recruited to induce tumor immune killing. ② Phenylboronic acid can enhance cellular nucleus uptake of acetylene progesterone probe, but its targeting Sia needs to be improved in vivo. Furthermore, based on the high expression of Sia on the surface of tumor cells, a novel Sia ligand guanidine phenylboronic acid (SBP) was synthesized in our lab. Cell fluorescence imaging showed that SBP can bind to Sia with high specificity and affinity, and animal PET imaging indicated that PET image quality is good with high radiotracer uptake in tumor and high ratio of tumor to background. Therefore, we will perform these studies in this proposal, as followed: 1. We will develop an immunotherapy agent (SBP-DNP) with DNP and SBP, and radiolabel SBP-DNP with 177Lu to obtain a multifunctional radioimmunotherapy agent (177Lu-SBP-DNP) targeting tumor Sia; 2. To test enhance the effect of combined killing tumor via an increase in the number of DNP on the surface of tumor cells mediated by SBP and apoptosis of tumor cells treated by 177Lu internal irradiation, in cellular and animal models levels; 3. To explore the mechanism and efficacy of combined immunotherapy and radiotherapy which were induced by 177Lu-SBP-DNP using ECT imaging and pathological analyses. We will achieve the goal of the integration of diagnosis and treatment, and inducing tumor regression with the minimum dose, and provide reliable experimental foundation for the development of a new tumor treatment method.